Dawn Brown and her two sons, Zayden, 5, left, and Zander, 9, were found dead in their Clearwater home Sept. 22. Reports released this week showed Brown likely tried to sedate the boys before drowning them.

CLEARWATER — Two boys killed in a September murder-suicide in a Clearwater home were drowned, the Pinellas-Pasco Medical Examiner's Office has determined.

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Autopsies on 9-year-old Zander and 5-year-old Zayden Brown showed that drowning was their cause of death, and the deaths were ruled homicides, according autopsy reports obtained Tuesday by the Tampa Bay Times.

Their mother, Dawn Brown, 34, committed suicide by hanging herself from a ceiling fan in the family's Clearwater home.

The Sheriff's Office announced soon after the discovery of the bodies that detectives suspected Dawn Brown had killed the children, then herself.

The Medical Examiner's reports released this week appear to support those initial findings and shed some new light on the circumstances of the boys' deaths.

Unusually high levels of diphenhydramine, a chemical compound found in antiallergy and sleep medications, in the blood of both boys suggest that their mother might have dosed them with an over-the-counter medicine to put them to sleep before they were killed. "Diphenhydramine intoxication" was ruled a contributing condition to the deaths of Zander and Zayden.

Absent more evidence, however, investigators can't be sure that Dawn Brown used a medication to make the children drowsy or render them unconscious before drowning them, said Pinellas County Sheriff's Office spokeswoman Cecilia Barreda.

"There was enough quantity (of diphenhydramine) there that it could have been a possibility," Barreda said. "We can't really say with 100 percent certainty."

The case is now considered closed, Barreda said.

She said the autopsy reports have not helped investigators formulate a more detailed picture of what might have transpired the night Dawn Brown and her children died.

Dawn Brown and her sons were discovered dead early Saturday, Sept. 22, by Murphy Brown, the boys' father and Dawn's husband, when he returned home from a poker game with friends. He said he found Zander and Zayden tucked into their beds at the family home on Sidney Street in Clearwater. Dawn was hanging by an electrical cord from a ceiling fan.

Murphy Brown could not be reached for comment Tuesday.

Family members said after the deaths that Dawn Brown had slipped into a severe depression worsened by financial problems, marital discord, and a criminal case filed against her over alleged welfare fraud.

The murder-suicide still came as a shock to Murphy Brown and other family members, who described Dawn as a caring mother who doted on her children.

A joint funeral service for all three was held in September, and they were buried in adjoining plots at Calvary Catholic Cemetery in Pinellas Park.

Peter Jamison can be reached at pjamison@tampabay.com or (727) 445-4157.